According to recent increasing of energy consumption, demand for alternative energy replacing fossil fuels has been rising as measures to cope with global warming. As a source of the alternative energy, solar cells have been attracted the attention and hence progressively developed. They are studied for various practical applications. From a practical viewpoint, it is particularly important to improve their flexibility and durability so that they can be installed on various places. However, single crystal silicon solar cells, which are the most basic solar cells, are expensive and it is difficult to produce flexible ones. On the other hand, organic solar cells and organic-inorganic hybrid solar cells, in which many researchers have been lately interested, have room for improvement in durability.
In addition to the above solar cells, other photoelectric conversion devices, such as organic EL devices and photosensors, have been also researched with the aim of improving their flexibility and durability. Those devices usually comprise indium-doped tin oxide (hereinafter, often referred to as “ITO”) in the form of films serving as transparent electrodes. The ITO films are normally formed by sputtering or the like. In order that the ITO films can have high electroconductivity, it is necessary to carry out the sputtering procedure at a high temperature and to anneal thereafter the formed films at a high temperature. However, it is often the case that organic materials cannot be subjected to those procedures at a high temperature.
Meanwhile, transparent electrodes in electronic devices can be made of ITO/Ag/ITO composite material, which has low electronic resistance and high transparency. There is an examination case in which the composite-material electrode is adopted in a device comprising a PEDOT/PSS layer. Even so, however, amorphous ITO (hereinafter, often referred to as “a-ITO”) and silver are liable to be deteriorated by acids or halogens diffusing from the outside or from other layers. Further, silver itself tends to easily migrate into other layers. If migrating into other layers, silver reacts with water or the like to produce silver oxide or the like, so that it may impair the transparent electrode. Not only that, but also the migrating silver may reach into the active area of the electronic device and consequently may lower the performance of the device.